Unable to update APS package list

As the subject syas. In the Apps & Addon packages page, clicking on the Update package list button does nothing. It used to work in some earlier version, maybe in 3.1 too, but it seems to be broken now. There is nothing relevant in /var/log/ispconfig/ispconfig.log or /var/log/ispconfig/cron.log or /var/log/apache2/error.log. I have a single repository, the default one (http://repo.ispconfig.org/addons/).

Well, connecting to repo.ispconfig.org (78.46.214.218) and trying the request the ISPConfig code is executing, I get the following. Looks like an empty result set. Should I set another repo or continue using this one? Is this a temporary error?